I. Field of the Invention
The present invention relates generally to automotive navigation systems and, more particularly, to a method for displaying traffic information in an automotive navigation system.
II. Description of Related Art
Automotive navigation systems have become increasingly prevalent in automotive vehicles. Such navigation systems typically include a display screen mounted in the vehicle in a position visible to the driver. Conventionally, such automotive navigation systems display a road map on the screen and, by using GPS to determine the position of the vehicle, also display the position of the vehicle on the screen.
Many roads, and certainly most major roads, include traffic sensors which detect the average vehicle speed at the position of the sensor on its given road as well as traffic events which potentially affect traffic flow. These traffic sensors transmit this traffic flow data to a central station. The central station, after combining the received signals from the various traffic flow sensors across the country, transmits the combined traffic flow data to a geographic area. For example, in the United States, traffic flow data for the contiguous 48 states is continuously transmitted by satellite.
There have been previously known navigation systems having receivers which receive the traffic flow data transmitted by satellite. These previously known navigation systems then compare the traffic flow data for the various road segments displayed on the navigation system display screen with preset speed limits corresponding to predetermined traffic flow conditions. For example, these previously known navigation systems may designate average vehicle speeds in excess of 55 miles per hour to constitute light traffic, traffic speeds between 30 miles per hour and 55 miles per hour to constitute light congestion, and all traffic speeds less than 30 miles per hour to constitute a congested traffic condition. The navigation system then generates the appropriate display on the display, e.g. by using different colors to represent different traffic flow conditions.
These previously known navigation systems having traffic flow display capabilities, however, all suffer from a number of common disadvantages. One disadvantage is that these previously known navigation systems fail to accommodate different drivers with different driving habits. For example, while one driver may consider a speed of 40 miles per hour to constitute a traffic flow with light congestion, a different driver with different driving habits may consider such a traffic flow condition to constitute a highly congested traffic flow condition. Still a third driver may consider such a speed to constitute a smooth traffic flow condition.
Similarly, these previously known navigation systems with traffic indication capability all fail to take into account traffic flow conditions which vary as a function of other driving conditions. For example, the geographic area in which a particular vehicle is driven, the weather conditions, day of the week, road type, as well as other factors, all impact on the traffic flow conditions. Because of this, the previously known navigation systems with traffic flow indicators have provided inadequate information to the driver of the vehicle for the driver of the vehicle to determine the actual traffic flow conditions for one or more road segments.
A still further disadvantage of these previously known navigation systems with traffic flow indication capability is that such systems are limited strictly to a display of the relative traffic congestion along the various road segments displayed on the display device. These systems, however, are unable to display other data to the driver in order to enable the driver to assess the actual road conditions. For example, various traffic events, such as a flooded road, road work, and the like, may greatly impact upon the road conditions and, correspondingly, the selected route by the driver. Still other information, such as information that the navigation system is currently receiving data from the satellite transmission and that the information displayed on the display screen is current, also impacts upon the route selection of the driver. These previously known systems, however, do not display such information.